1. Field of the Invention
The present general inventive concept generally relates to an image forming apparatus and a fixing unit control method thereof, and more particularly, to an image forming apparatus and a fixing unit control method thereof in which a relay unit is provided for hardware control of a fixing unit, and power supplied to the fixing unit is controlled in accordance with on/off operations of the relay unit.
2. Description of the Related Art
An image forming apparatus forms an image to be printed on a printing medium. The image forming apparatus may be embodied in a printer, a copy machine, a facsimile, a multi-function peripheral having two or more functions, etc.
Specifically, the image forming apparatus forms an image by an image forming unit which includes an image carrying body, an optical scanning unit to scan a beam to the image carrying body to form an electrostatic latent image, a developing unit to develop a toner image corresponding to the latent image formed on the image carrying body, and a transfer unit to transfer a toner developed on the image carrying body and charged with electricity to the printing medium.
An image transferred to the printing medium is thermally pressed by the fixing unit and discharged to the outside. The fixing unit is heated with supplied power and fixes the image on the printing medium.
The image forming apparatus is provided with a temperature sensing unit (or a temperature sensor) that senses temperature of the fixing unit in order to prevent the fixing unit from overheating, and controls power supplied to the fixing unit on the basis of sensing results.
The temperature sensing unit includes a thermistor contacting a fixing roller of the fixing unit and senses the temperature. The temperature of the fixing unit is controlled depending on the resistance of the thermistor.
For example, the image forming apparatus receives a resistance level of the thermistor varied depending on the temperature, and outputs a signal for controlling the fixing unit in accordance with the temperature of the target, thereby controlling the fixing unit to maintain proper temperature.
However, the temperature of the fixing unit may be abnormally controlled by noise and static of power supplied from the exterior, reliability of peripheral parts, and the like problems. Thus, there is a need of an additional safety device to prepare for an abnormal state of the fixing unit.